For processing data by a portable data carrier provided with a processor, which are provided to this data carrier by an external device, the data carrier has write functions, which write the data into a specific memory area of a non-volatile memory of the data carrier, for example into an EEPROM memory of a chip card. This is the case, for example, with chip cards and smart cards, which are used for transactions at a terminal of a point of sale or of a credit institution. Usually, such data are written bitwise on the basis of a memory address into a target file of the data carrier. Such write commands for chip cards standardized according to ISO-IIC 7816-4 are, for example, UPDATE-BINARY and WRITE-BINARY.
In most cases the data provided to the data carrier are not longer than 256 bytes. If the operation of transferring the data onto the data carrier is interrupted, for example by an interruption of the power supply, a memory area of 256 bytes has to be deleted in order to avoid data inconsistencies and to ensure the integrity of the data carrier. This applies in particular to chip cards because data are stored by applying charges on capacitors, and the writing of data bits into the EEPROM memory in case of certain write commands can depend on the bits to be overwritten or the current energy level of the capacitors. Since the most non-volatile (EEPROM) memories are organized in pages of 64 bytes, for the data deletion a time requirement of 3 ms×256/64=12 ms is typical. Such time requirement is still acceptable with contactlessly operated chip cards. But when storing large data records, the time required for deleting the respective memory area can be unacceptably long. For a data record of 8 kilobytes a delete time of already 8192/64×3 ms=384 ms is required.
EP 0 811 204 B1 describes a method for storing data in a chip card, wherein before a processing of the data by the chip card an access authorization is checked and before the check of the access authorization the data are temporarily stored in a memory area provided therefor. EP 0 914 640 B1 discloses the storage and use of security-critical information in a data carrier, wherein the data are protected against unauthorized access by encrypting with temporary keys before they are used. But none of the above prints offers a solution for the problem of a too long delete time in case a write process is interrupted.
Therefore, the invention is based on the problem of proposing a method for the secure processing of data and a corresponding data carrier, wherein the deletion of memory areas is carried out in an accelerated fashion.